Next Generation mobile networks, such as Fifth Generation (5G) mobile networks, are expected to operate in the higher frequency ranges, and such networks are expected to transmit and receive in the GigaHertz band with a broad bandwidth near 500-1,000 MegaHertz. The expected bandwidth of Next Generation mobile networks is intended to support download speeds of up to about 35-50 Gigabits per second. The proposed 5G mobile telecommunications standard, among other features, operates in the millimeter wave bands (e.g., 14 GigaHertz (GHz) or higher), and supports more reliable, massive machine communications (e.g., machine-to-machine (M2M), Internet of Things (IoT), etc.). Next Generation mobile networks, such as those implementing the 5G mobile telecommunications standard, are expected to enable a higher utilization capacity than current wireless systems, permitting a greater density of wireless users, with a lower latency. Next Generation mobile networks, thus, are designed to increase data transfer rates, increase spectral efficiency, improve coverage, improve capacity, and reduce latency.
Millimeter wave (mmWave) frequencies are proposed to be used in advanced wireless systems, such as, for example, 5G systems. mmWave frequencies, however, have limited building penetration as compared to lower frequency waves. Due to this limited building penetration, cell sites containing the system antennas will need to be close to the network user to make up for the signal losses through buildings. This requires a greater cell density in the advanced wireless systems, relative to current systems. Additionally, to satisfy the improved utilization capacity requirements of advanced wireless systems, a greatly increased number of antennas, relative to current systems (e.g., Fourth Generation (4G) systems), will need to be deployed to support high bandwidth connections to each wireless device. In current wireless systems, the typical distance between adjacent antennas is about 1.5-3.2 kilometers (km). In contrast, for proposed advanced wireless systems, such as 5G systems, the distance between adjacent antennas may need to be reduced to about 200-300 meters. Therefore, next generation wireless systems may need as many as one hundred times the number of antennas as compared to current wireless systems.
Multiple-input and multiple-output (MIMO) is a technique for using multiple transmit and receive antennas to multiply the capacity of a radio link and exploit multipath propagation. MIMO is a component of wireless communication standards such as Wi-Fi (IEEE 802.11n & IEEE 802.11ac), WiMAX (4G) and Long-Term Evolution (4G). Full dimension MIMO (FD-MIMO) involves multiple transmit and receive antennas that can form beams in both horizontal and vertical directions such that the beams can cover anywhere in three-dimensional space in the vicinity of the multiple antennas. Massive MIMO involves a MIMO system that utilizes a very large number of antennas. The more antennas a massive MIMO system has, the more possible signal paths the system has and the better the system's performance in terms of data rate and link reliability.